Tagged Questions

A black hole is a volume from which photons, or any matter, can not escape. More formally, the coordinate speed of light at the event horizon - the boundary of a black hole - is zero, as measured by a sufficiently separated observer.

Assume two black holes in the most common size range, spiraling into each other until they merge. The event releases significant amounts of energy via gravitational waves, which warp the space-time.
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I know the question has been asked about how an event horizon is distinguishable from a singularity given that time must come to a stop at the event horizon, but I haven't been fully satisfied by the ...

When just considering GR without evaporation nor QM, is an empty (containing no matter or anything) black hole possible ?
Let's say that there is only GR and nothing else (no matter or boson fields), ...

I was just thinking about this the other day. Given Einstein's Relativity etc. assigning the cosmic "speed limit" the value of $c=299792458\:\frac{m}{s}$, we know that the event horizon is the point ...

This came to me after reading that a black-hole that has the mass of the observable universe will also have an event horizon that covers the observable universe.
Since the definition of a black hole ...

An (unlikely) charged black hole can be described with the mass, angular momentum, charge and the thermal radiation. The reasoning behind the thermal radiation rests on the particle creation outside ...

In the Kerr solution to the vacuum Einstein Equation written in Boyer–Lindquist coordinates. Because it is not spherical polar coordinates, $r$ ranges from 0 to infinity does not cover all the space, ...

The low-energy bosonic effective actions of string theory lead to Einstein-Hilbert gravity, along with scalars and $p$-form Maxwell fields. For example, the action for type IIA string theory is
$S = ...

If something is caught in the pull of a black hole and keeps accelerating it can't keep accelerating with no limits or else it would accelerate beyond c. So is there a limit on how fast acceleration ...

The repartition of dark energy in the vacuum is homogeneous all over the universe. The diagram below represents space with a black hole in the middle. The square is divided in small unit squares. If ...

Would would happen if you started pumping charged particles of same charge into a black hole? Let's assume that you have an infinite number of those charged particles. What will happen to the event ...

If the Schwarzschild metric is suppose to describe the behaviour of a spherical object in flat space, so the Schwarzschild is different from the flat metric because it describes curved space so why ...

I understand that one of the simplified ways of looking at Hawking radiation is a pair of virtual particles close to the event horizon (but outside of it). The particle with negative energy falls into ...

Suppose at time $t$, Alice and Bob are hovering just outside the event horizon of a black hole, sharing the same position, velocity and acceleration. Shortly afterward, in less than the Schwarzschild ...

I'm think that in general relativity we can always pass the one curve in one coordinate system for another coordinate system. My intuition say that the free falling observer locate the event horizon ...

First of all, I'm not interested in time for this question. So lets consider a 3-manifold whose metric is the spatial part of the Schwarzschild metric, so it has the event horizon and the singularity ...

What if when a supernova occurs, instead of it condensing into a singularity it creates enough force to tear a hole into the fabric of space? Is a black hole just what is sounds like, a hole in space? ...

By dumping a gas cloud into a small black hole, I can produce radiation energy, this is how quasars produce energy.
By dumping the previous black hole, with the gas cloud inside, into a black hole, ...

When two black holes collide, if the singularities were very small they would never merge together. they would rotate very fast as something other than a disk. The event horizon would oscillate very ...

As an offshoot of the question Can we have a black hole without a singularity? I'm curious if the point of no return at which the massive object is condemned to become a singularity happens before its ...